Photographic material containing yellow fog-preventing agents



United States Patent 8 Claims. ((51. 96-84) ABSTRACT OF THE DISCLOSUREYellow fog formation in silver halide emulsion supports, particularlywhere the support surface is a baryta layer, can be avoided by adding tothe emulsion or baryta layer or both a heterocyclic compound having a 5to 6 membered nitrogen-containing heterocyclic ring substituted with amember selected from the group consisting of esterified carboxyl andesterified thiocarboxyl, said substituent being directly bonded to aring nitrogen, or through only a sulfur or oxygen atom to a ring carbonin alpha position to a ring nitrogen, said heterocyclic compound beingcapable of splitting off said substituent and forming diflicultlysoluble silver compounds.

This invention relates to an improved photographic material comprising asilver halide emulsion layer and containing an organic compoundpreventing the formation of yellow fog.

In the processing of photographic materials, thiosulfate is frequentlytransferred from the fixing bath into the developer. On other occasions,such as when using highspeed, stabilizing or fixing developers, a silverhalide solvent, generally thiasulfate, is added to the developer. Whensuch developers containing silver halide solvents are used in thedevelopment of photographic materials, a yellow to brown fogging isproduced, of varying intensity depending on the type and the age of thephotographic paper. In the presence of many stabilizers, e.g.l-phenyl-S-mercapto-tetrazole, this fogging may also be blue to bluishviolet in color. With photographic papers, this fogging is due to finelydivided silver deposited in the baryta-coating.

This yellow fogging produced with baryta-coated photographic papersresults from the passing, during the casting process, of silver saltsfrom the silver halide emulsion into the baryta coating Where they areadsorbed by the baryta. During the storage of the papers, these silversalts are reduced to silver, particularly in the first months ofstorage. If the developer used in the processing of such papers containssilver halide solvents, such as thiosulfates, the dissolved silver saltsare reduced on the silver nuclei of the baryta and a yellow fogging andspot formation is produced. Furthermore, the properties of the startingmaterials play a large part in the formation of spots or stains.

After storage, the yellow fogging appears particularly strongly at thoseareas of the papers which were exposed to the humidity of the air, ie atthe edges of the papers and on the uppermost sheet of a pack.

This yellow fogging occurs particularly when using unwashed silverchloride or chlorobromide emulsions because the chlorides present inexcess are able to form soluble silver complex salts.

This yellow fogging also occurs if, in the production of the emulsion orthe baryta, types of gelatin are used which contain compounds capable ofdissolving silver halide and if in addition nucleus-forming degradationproducts of the gelatin are present. Such types of gelatin also causewhich is capable of a yellow fogging with photographic films. Inaddition, emulsions which have only just ripened and have a steepgradation are particularly liable to produce yellow fogging when steeplyoperating developers with a relatively high content of potassium bromideare used for developing the silver image.

It has now been found that yellow fogging can be avoided by usingphotographic materials which contain in a hydrophilic, water permeablecolloid layer, e.g. the silver halide emulsion layer and/or the barytacoating, substances of the following general formula:

wherein R represents a nitrogen-containing heterocyclic ring system, Xrepresents sulfur or oxygen bonded to a carbon atom of the heterocyclicring, R represents alkyl, cycloalkyl, aryl, aralkyl and Z. representsoxygen or sulfur.

In the above formula suitable heterocyclic ring sys tems R are the ringsystems of diazoles, oxazoles, triazoles, imidazoles, thiazoles,thiadiazoles, thiadiazolidines, oxadiazoles, tetrazoles, diazines,triazines, imidazolines, benzthiazoles, benzoxazoles, benzimidazoles,naphtriazoles, benztriazoles, quinoline, pyrimidine, partiallyhydrogenated pyrimidine, quinazoline, quinoxaline, purine,azaindolizines or other heterocyclic ring systems which form part ofheterocyclic compounds that are capable of forming diflicultly solublesilver salts and which are used in the photographic art as stabilizersor antifoggants for silver halide emulsions. The heterocyclic ringsystems are derived from said heterocyclic compounds by subtractingtherefrom a mercapto or hydroxy group which is bonded to theheterocyclic system or by subtracting therefrom a hydrogen atom which isbonded to nitrogen atom forming part of the heterocyclic system.

A suitable class of compounds may more specifically be represented bythe following formula:

wherein Y represents S, NH, or a chemical represents sulfur or oxygen,11 represents an integer from 0 to 10, and R has the same meaning as inFormula I.

Representative of this class of compounds are the following:

bond, X2

wherein R represents alkyl having 1 to 18 carbon atoms, cycloalkyl orcarboxyalkyl, preferably up to 5 carbon atoms, X represents S, NH or achemical bond, X represents S, NH, N-alkyl, N-alkenyl or and Z and Rhave the same meaning as in Formula I.

3 A Representatives of this last mentioned class of compounds are:

X2 X1 Z R2 R1 l.P.,

S S methyl ethyl 38 S S '0 methyl methyl 41 S S 0 methyl phenyl 57 S S Oethyl ethyl 39 S S O ethyl methyl 41 S S O ethyl phenyl 52 S S On-pi'opyl ethyl Fluid S S O lsopropyl ethyl Fluid S S 0 sec. butyl ethylFluid S S O n-butyl ethyl S S O n-butyl methyl Fluid S S O n-butylphenyl Fluid S S S n-butyl ethyl Fluid S S S n-butyl phenyl 58 S S On-pentyl ethyl Fluid S S O n-pentyl methyl Fluid S S O n-hexyl ethyl 39S S O n-octyl ethyl 33 S S O n-octyl methyl S S O n-oetyl phenyl (1) S SO (|TOCzII5 ethyl 81 0 27 S NH O n-clodecyl ethyl 67 28 S NH Ocyclohexyl ethyl 129 29 III chem. bond 0 methyl ethyl 75 30 III chem.bond 0 methyl phenyl 142 31 N chem. bond 0 methyl ethyl (1) JHz-CH=CHz32 N chem. bond 0 methyl phenyl 78 eH2CH=oHi 33 chem. bond 0 methylethyl 89 1 Highly viscous fluid.

Further specific examples of suitable compounds are those of thefollowing formulae: 89 N N t .l 34"- -I |III II M.P. 92 C. N\/O-S(TOCQHB 1 S 0 CSC-OC2Hs N O 35 N M.P. 65 0.

S SC-OC2H5 H II N 0-sc-0- 0 ll l lI O as." M.P. s9" 0.

O SCO-C H 41-.- 5 4 N l 37... M.P. 46 C. L N 3N N SCOC2H5 2 I OzH5O-C-SN t 0 0 (3-OC2H5 O 42--- 0 3s O4gN M.P.79C. 7

1 l H N Q e 0 s c o c 11 I 5 CO-C21I M.P. 48 C.

M.P. 50 C.

M.P. 143 C.

M.P. 86 C.

My. 78" c.

Ml. 154 c.

Ml. 41 C.

Highly viscous fluid.

MP. 59 C.

Fluid.

Highly viscous fluid.

Ml. 79 C.

Highly viscous liquid.

Fluid.

The compounds may be produced by reaction of about equivalent amounts ofthe heterocyclic compounds containiug either a hydrogen atom bonded to aheterocyclic nitrogen atom or a mercapto or hydroxy group bonded to acarbon atom of the heterocyclicnucleus with chloroformic orchlorothioformic acid esters in the presence of sodium hydroxide inacetone or dioxane at temperatures of 040 C. The crude products whichare not soluble in ether are purified by Washing with water andrecrystallizing. The other crude products are dissolved in ether andafter evaporation of the ether recrystallized from suitable solvents.These processes are illustrated by the following examples.

Production of compound 23.-26.2 g. mol) of2-octylthio-5-mercapto-1,3,4-thiodiazole are suspended in 40 cc. of 10%sodium hydroxide solution with addition of 300 cc. of acetone. 9.6 cc.mol) of ethyl chloroformate are added to the suspension with stirring at0 to 5 C. After distilling off the acetone, the residue is extractedwith ether. The ethereal solution is washed neutral, dried, and theether distilled off. The crude product is recrystallized from methanol.Yield 17 g'. Melting point 33 C.

Production of compound 56.--l5 g. of 6-methyl-4-hydroxy-l,3,3a,7-tetraazaindene are suspended in cc. of acetone withaddition of 20 cc. of 20% sodium hydroxide solution. 9.6 cc. of ethylchloroformate are added to the suspensoin with stirring at 0 to 5 C.After distilling oil? the acetone, the residue is purified by washingWith ether and recrystallized from acetone. Yield 4.2 g. Melting pointC.

Compound 42 is set out in Beilstein, vol. 26, page 40.

Methanol is used for recrystallizing compounds 1, 9, 10, 15, 16, 22, 24,26, 27, 28, 29, 38, 39, 44, toluene for recrystallizing compound 2 andpetrolether for recrystallizing compound 8. Compounds 6, 7, 35, 36, 43are purified by dissolving the raw products in ether, washing theethereal solution with water, evaporating the ether, dissolving theresidue in methanol and precipitating with water. The raw product ofcompound 3 is purified by dissolving it in Inethylenechloride,evaporating the solvent, reprecipitating the residue fromdimethylformamid and water and dissolving the precipitate in ether andevaporating the ether. The raw products of compounds 4 and 5 are firstdissolved in methylenechloride, the methylenechloride is evaporated, theresidue is redissolved in petrolether and the solvent is evaporated. Theraw products of compounds 11, 12, 13, 14, 17, 18, 19, 20, 21, 25, 31,33, 34, 37, 40, 45, 46, 47, 49, 50, 51, 52, 53, 57 are purified bydissolving them in ether, washing the ethereal solution with water,evaporating the ether, redissolving the residue in ether, methanol andacetone and each time evaporating the solvent. The raw products ofcompounds 30, 54 are purified by dissolving them in methylenechloride ordioxane respectively and evaporating the solvent.

The substances of the present invention are probably not adsorbed by thesilver halide grains of the emulsion, but are disposed in the gelatinphase between the silver halide grains. In the alkaline developer, thecarboxy group is split off and the compound reacts with the solublesilver salts, thus preventing the formation of yellow fogging.

As silver halide emulsion, it is possible to use emulsions containingsilver chloride or silver bromide or mixtures thereof. Furthermore, theemulsion may contain up to about of silver iodide, as calculated ontotal silver halide.

As binding agents for the baryta layer can be used animal gluespreferably gelatin which may be partially replaced by film-forminghydrophilic products such as polyvinyl alcohol, polyvinyl-pyrrolidone,alginic acid or derivatives thereof such as alkali metal salts, estersin particular with lower aliphatic glycols, or amides, and in addition,carboxyethylcellulose, starch or the like. As baryta pigment can be usedmineral products such as processed heavy spar or artificial productssuch as permanent white or blanc fixe.

The compounds according to the invention can be added to any desiredlayer of the photographic material, but advantageously to the barytaand/ or light-sensitive silver halide emulsion layer. It will depend onthe photographic material and the compound in which layer the optimumefficacy is achieved. However, this can be established by a few simpleexperiments without any difficulties.

The same applies as regards the concentration to be used. The quantitiesto be added depend on the layer in which the compounds are incorporatedand this can also be established by simple tests. When used in theemulsion layer, the compounds are added in amounts of about 2-300 mg.,advantageously 5-60 mg. per mol of silver halide. For the baryta layer,concentration of 0.0.ll.0 g./l. and advantageously 0.050.15 g./l. ofcasting solution are suitable. These amounts correspond to 0.022 mg,preferably 0.04-0.3 mg. per gram of barium sulfate.

The compounds according to the invention can be added at any time, butadvantageously to the prepared casting solution.

The photographic emulsions can be either sensitized or non-sensitizedoptically. In addition, other chemical ripening compounds can also beadded to them, for example sulfur compounds or noble metal salts. Theemulsions can further contain alkylcne oxide polymerization products aschemical sensitizers. Moreover, the new stabilizers can be used togetherwith other stabilizers which are already known. They can furthermore beused in 8 emulsions which contain color couplers or silver halidedeveloper substances.

In the processing of the photographic materials according to theinvention, it is possible to employ the conventional developercombinations. The process does not depend on any particular developersubstances. It is for example possible to use as developer substanceshydroquinone, pyrocatechol, p-methylaminophenol, 1-phenyl-3-pyrazolidones or phenylene diamines.

Example 1 An unrinsed silver chlorobromide emulsion containing 0.12 molof silver halide per litre, has added thereto, prior to casting, 2 mg.of compound 15 dissolved in alcohol. After adding the conventionalhardening and wetting agents, the emulsion is then applied in knownmanner to a baryta-coated paper and dried. The paper, both when freshand after being kept for 2 days in a hot cupboard at 60 C., wasdeveloped for 1, 2, 3, 5 and 7 minutes at 30 C. in ap-methylaminophenol-hydroquinone developer, to which 10 g./l. ofcrystallized sodium thiosulfate had been added in order to test foryellow fogging. Whereas the specimen showed no yellow fogging, evenafter storage in the heated cupboard, a control specimen when freshshowed a slight yellow fogging, and after being kept in the cupboard astrong brownish-yellow fogging was visible, even after a developmenttime of 1 minute. If the emulsion layer is removed from the barytacoating, it is seen that the baryta coating of the control specimen isbrown in colour and that of the test specimen is colorless.

Instead of compound 15 referred to above, the following can also beadded to the emulsion with the same result:

20 mg./1. of compound 16, 20 mg./l. of compound 23, 5 mg./l. of compound37, 15 mg./l. of compound 42 or 15 mg/l. of compound 35.

Example 2 One liter of silver chloride emulsion, containing 0.08 mol ofsilver halide, has 5 mg. of compound 39, dissolved in alcohol, addedthereto prior to casting. After adding the usual hardening and wettingagents, the emulsion is then applied in known manner to a baryta-coatedpaper and dried. The test for yellow fogging is carried out as describedin Example 1. Whereas the control specimen shows a bluish-yellow foggingafter being kept in the heated cupboard, no fogging is visible with thespecimen according to the invention. Instead of the aforementionedcompound 39 it is also possible for 5 mg./l. of compound 36 or 10 mg./l.of compound 52 to be added to the emulsion with the same result.

Example 3 A phototechnical emulsion, which contains about 0.4

mol/L of silver halide (silver iodobromide emulsion), has 5 mg. ofcompound 56, dissolved in alcohol, added thereto prior to casting. Afteradding the usual hardening and wetting agents, the emulsion is appliedin known manner to a film or paper support and dried. The test foryellow fogging is carried out as described in Example 1. The specimendoes not show any yellow fogging, Whereas a yellow fogging is visible onthe control specimen after being stored in the heated cupboard.

Instead of the aforementioned compound 56, it is possible with the sameresult to add to the emulsion 1 mg./l. of compound '28.

Example 4 A baryta-coating solution has added thereto 0.15 g./l. of thecompound 2, dissolved in alcohol, and a paper is baryta-coated therewiththree times in known manner. An unrinsed silver chlorobromide emulsionis thereafter applied to this paper in known manner. The baryta-coatingsolution may be obtained in known manner from 15 kg. of barium sulfate(containing 20% of water), 1.5 kg. of gelatin in the form of a 5%aqueous solution, cm. of a 20% aqueous sodium hexametaphosphatesolution, 300

cm. of a 10% aqueous chrome alum solution and 200 cm. of milk. Insteadof compound 2 the baryta coating solution may have added thereto perliter 30 mg. of compound 10, 12 or 15, 20 mg. of compound 28 or 50 mg.of compound 35.

The test for yellow fogging is carried out as described in Example 1.Whereas the experimental samples shows no yellow fogging after theheated chamber storage, a dark brown patchy yellow fogging is visiblewith the control specimen.

What I claim is:

1. A photographic material comprising a support carrying a lightsensitive silver halide emulsion layer, said emulsion being in contactwith a heterocyclic compound having a to 6 membered nitrogen containingheterocyclic ring substituted with a member selected from the groupconsisting of esterified carboxyl and esterified thiocarboxyl, saidsubstituent being bonded directly to a ring nitrogen, or through only asulfur or oxygen atom to a ring carbon in a-position to a ring nitrogen,said heterocyclic being capable of splitting off said substituent andforming difficultly soluble silver compounds and being present in amountsufiicient to substantially inhibit the formation of yellow fog.

2. A photographic material according to claim 1, wherein said support iscoated with a baryta layer which is arranged between said support andsaid silver halide emulsion layer.

3. A photographic material according to claim 1, wherein saidheterocyclic ring contains 1 to 4 nitrogen atoms.

4. A photographic material according to claim 1, wherein saidheterocyclic ring is a five membered ring containing one to two nitrogenatoms and a sulfur atom.

5. A photographic material according to claim 1, wherein saidheterocyclic ring contains a nitrogen and an oxygen atom.

6. A photographic material comprising a support, a baryta layer and asilver halide emulsion layer, the baryta layer being arranged betweenthe support and the silver halide emulsion layer, at least one of saidlayers containing a heterocyclic compound of the formula O X: X:wherein:

R is a member of the group consisting of alkyl having 1 to 18 carbonatoms, cycloalkyl, aryl and aralkyl,

Y a member of the group consisting of sulfur, oxygen and nitrogen;

X a member of the group consisting of sulfur and oxyrz an integer of 0to 10; and

m an integer of 0 to 1.

wherein:

R is a member of the group consisting of alkyl having 1 to 18 carbonatoms, cycloalkyl, aryl and aralkyl; R is a member of the groupconsisting of alkyl having 1 to 18 carbon atoms, cycloalkyl, andearboxyalkyl; X is a member of the group consisting of sulfur andnitrogen; X is a member of the group consisting of S, NH, N-al kenyl and/alkyl \alkyl the alkyl groups having 1 to 6 carbon atoms; and Z is amember of the group consisting of sulfur and oxygen,

said heterocyclic compound being present: in amount sufficient tosubstantially inhibit the formation of yellow fog. 8. A photographicmaterial according to claim 1 in which the heterocyclic ring is athiodiazole ring and the substituent is connected through a sulfur atomto a ring carbon.

References Cited UNITED STATES PATENTS 2,760,933 8/1956 Fields et a1260-302 2,939,789 6/1960 Dersch et a1 96-109 3,212,892 10/1965 Konig etal 96129 NORMAN G. TORCHIN, Primary Examiner. J. H. RAUBITSCHEK,Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,364,028 January 16, 1968 Anita von Konig It is certified that errorappears in the above identified patent and that said Letters Patent arehereby corrected as shown below:

Column 1, line 36, "thiasulfate" should read thiosulfate Column 2, lines67 to 69, the formula should appear as shown below: k

a1 yl c alkyl Column 5, formula 50, the right-hand portion reading -C Hshould read C I-I Column 6 formula 54 "M.P. 143 C." should read D.P, 143C. line 72, "suspensoin" should read suspension Column 9, lines 43 to45, the right-hand portion of the formula reading I I IIS-C-OR shouldread lI-S-C-OR Column 10, lines 14 to 16, the right-hand portion of theformula should appear as shown below:

C-S-Ci-Z-R Signed and sealed this 18th day of November 1969.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. Attesting OfficerCommissioner of Patents

